Inverted (p-i-n) perovskite solar cells have emerged as a highly promising next-generation photovoltaic technology due to their low-temperature processability, excellent device stability, and compatibility with commercial silicon bottom cells for tandem structures. Currently, high-efficiency lab-scale devices predominantly rely on small-area spin-coating processes in inert gas environments. Transitioning this technology to large-scale industrial production in ambient air is a key direction for achieving sustainable solar energy utilization.

However, the industrialization of perovskite photovoltaics remains constrained by the dual bottlenecks of scalable fabrication and long-term operational stability. During blade-coating in ambient air, environmental moisture and oxygen readily interfere with the crystallization and microstructure of perovskite films. More critically, existing hole transport materials struggle to simultaneously achieve efficient charge transport, robust substrate anchoring, and favorable solution wettability. Conventional small-molecule self-assembled monolayers fail to achieve uniform conformal coverage on textured silicon substrates, while conventional polymers impede ink coating due to excessive hydrophobicity, leading to cumulative interfacial defects and significantly accelerated device degradation.

To address the above issues, a joint team comprising Nanjing University, Georgia Institute of Technology, The Hong Kong University of Science and Technology, among others, conducted in-depth research using ZEPTOOLS' JS series stylus profilers. The team innovatively designed and synthesized a copolymer hole transport material, PNCC, incorporating both triarylamine and carbazole phosphonic acid units. This effectively balanced high conductivity, strong interfacial anchoring, and favorable solution wettability, successfully enabling the scalable fabrication of high-efficiency, highly stable single-junction cells, modules, and perovskite/silicon tandem solar cells in ambient air.

Title: Scalable ambient fabrication of single-junction and perovskite–silicon tandem solar cells 
Journal: Nature Sustainability 
URL: https://doi.org/10.1038/s41893-026-01916-6

The research focuses on developing novel hole transport layer materials suitable for ambient-air fabrication to overcome the key bottleneck of balancing conductivity, wettability, and interfacial anchoring strength in inverted perovskite solar cells. Addressing the limitations of conventional small-molecule self-assembled monolayers, which tend to agglomerate and have narrow processing windows, and conventional polymers with excessive hydrophobicity, the team designed and synthesized a novel copolymer hole transport material, PNCC. By copolymerizing triarylamine monomers with carbazole phosphonic acid units, steric hindrance suppressed the cyclization side reactions of carbazole units during polymerization, significantly enhancing polymer molecular weight and charge carrier mobility. Simultaneously, the densely distributed phosphonic acid groups along the molecular chains formed strong multi-point chemical bonding with the transparent conductive oxide substrate, substantially improving interfacial adhesion and reducing surface roughness, effectively enhancing the spreading and wetting characteristics of the perovskite precursor ink on the substrate, thereby establishing a microscopic interfacial foundation for fabricating high-quality perovskite films.

In the implementation of ambient scalable blade-coating processes and the investigation of thin-film microstructural properties, precise control over the nanoscale thickness and spatial uniformity of functional layers is a critical prerequisite for ensuring efficient carrier extraction. The research team systematically advanced blade-coating fabrication in an open-air environment with approximately 40% relative humidity, employing ZEPTOOLS' JS series stylus profilers for precise measurement and calibration of the fabricated functional film thicknesses. The measurement data accurately confirmed that the deposited PNCC films maintained a stable thickness of 9–10 nm, with the perovskite absorber layer thickness at approximately 800 nm. Through rigorous characterization of film physical dimensions using ZEPTOOLS' JS series stylus profilers, the team verified that this material exhibits excellent flatness and coverage even at nanoscale film thicknesses. This not only endows devices with a wider processing window compared to traditional monolayer approaches but also provides a reliable film structural basis for elucidating the interfacial deep-level trap passivation mechanisms.

Addressing the power conversion efficiency and long-term operational stability of single-junction inverted perovskite solar cells and modules, the study delved into the microscopic mechanism by which the novel hole transport layer suppresses non-radiative recombination. Under fully ambient blade-coating conditions, PNCC-based single-junction cells achieved a power conversion efficiency of 26.6% with a voltage deficit as low as 0.30 V, and large-area photovoltaic modules with an active aperture area of 19.11 cm² attained a high efficiency of 23.2%. Multiple characterization techniques confirmed that this material significantly reduces the deep-level trap density at interfaces, promoting uniform luminescence and charge extraction. In operational durability tests, encapsulated devices maintained 99.8% of their initial efficiency after 1200 hours of continuous full-spectrum illumination at 40°C under maximum power point tracking. They also exhibited exceptional weather resistance under elevated temperatures of 65°C and 85°C, as well as under UV accelerated aging tests, effectively overcoming the technical bottleneck of rapid degradation in ambient-air-fabricated devices.

Addressing the industry pain point of achieving conformal coverage on micron-sized pyramidal textured surfaces in perovskite/silicon tandem cells, the research successfully extended the application of this copolymer material to monolithic two-terminal tandem cell architectures. Conventional self-assembled monolayer materials are prone to aggregation-induced defects on rough silicon surfaces, typically necessitating complex bilayer sputtered nickel oxide interlayers. In contrast, PNCC, leveraging its superior film-forming properties, achieved intimate, aggregation-free conformal coating directly on textured silicon substrates. As an independent hole transport layer, this material not only effectively suppressed phase segregation in the wide-bandgap perovskite top cell but also, under a simplified architecture without additional interlayers, achieved a certified tandem cell efficiency of 33.0%, retaining 85% of its initial efficiency after 1140 hours of continuous illumination at 65°C. This achievement significantly simplifies the processing steps for high-efficiency tandem devices, offering a solution of both academic value and industrial feasibility for the large-area, low-cost, and highly stable next-generation photovoltaic manufacturing.

ZEPTOOLS' JS series stylus profilers, as representatives of domestically manufactured high-precision surface measurement equipment, leverage their innovative technological architecture, flexible application scenarios, and reliable measurement performance. They are capable of measuring film thickness and step height, surface morphology, surface waviness, and surface roughness of micro- and nanostructures. They find wide applications in universities, research laboratories and institutes, semiconductor and compound semiconductor industries, high-brightness LEDs, solar energy, MEMS, touch panels, automotive, medical devices, and other sectors. As a breakthrough achievement in domestic scientific instrumentation, the JS series stylus profilers have broken the long-standing monopoly of foreign brands in the high-end surface measurement equipment market. With their high cost-performance ratio and localized service advantages, they have become the preferred equipment for domestic universities, research institutions, and manufacturing enterprises.